animated tiles?

per-layer/per-sprite effect data
font "layers", sort all layers (bitmap, font, tile) in one group, sprites get a sort and appear above that layer
FILE formats?
code to take something colliding with something else and "move it out" (for getting stuck in walls)
function to get the slope of the line you're colliding with
sliding functions?
FILE STORAGE libraries, you can export any portions of a world to it, import likewise, edit likewise, just like a game except doesn't need all the parts and can't be run


Collision proximity discards:
  Need a routine that's consistently effective for ~200 collisions per frame among objects of varied sizes distributed
  evenly across the scene/screen, all moving (approximately 50 objects of various types- not all registered to collide
  with all others- example, 12 enemies, 25 enemy bullets, 1 player, 12 player bullets = 12 + 25 + 144 = 181 collisions)
